1,1

Least number which becomes prime or 0 or 4 after n-1 iterations of f(x) = sum of prime factors of x (cf. A001414). Agrees with A048133 except for the second term.

A002217(61859965801) = 19, hence a(19) <= 61859965801.

A002217(3154858254831) = 20, hence a(20) <= 3154858254831.

A002217(6309716509658) = 21, hence a(21) <= 6309716509658.

A002217(44168015567557) = 22, hence a(22) <= 44168015567557.

Cf. A002217, A001414, A048133.

Adjacent sequences: A121357 A121358 A121359 this_sequence A121361 A121362 A121363

Sequence in context: A137370 A102735 A088960 this_sequence A047688 A089925 A120945

nonn

Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Jul 27 2006